颅面部生长发育

◆ A backward transposition of the ramus, thereby permitting elongation of the body of the mandible. ◆ A displacement of the body (and dentition) in an anterior direction. ◆ A vertical lengthening of the ramus, providing
下颌骨的生长发育
The Growth and Development of Mandible
口腔正畸学教研室 刘月华
Department of Orthodontics Liu Yuehua, DDS, PhD, M.Orth.RCS(Edin)
下颌骨的发生（Sperber，GH， 1989）
Three major parts: body, rami, alveolar process
◆ 颏部是骨改建的结果；
◆ 颏部对侧面外形具有重要意义。
四、牙列与合的发育
（一）合的建立
◆ 婴儿在无牙齿萌出时，无合关系；
◆ 婴儿第６个月乳牙萌出时开始建合；
◆ 成人第三磨牙萌出时才完成建合。
（二）建合的动力平衡（肌肉）
◆ 向前的动力 ◆ 向后的动力 ◆ 内外的动力平衡 ◆ 垂直向的动力平衡
Mandible symphysis closes 1-2 years.
下颌骨的三向生长
生长方式： ◆髁突软骨成百度文库 ◆骨膜下的骨表面增生
The mandible is a composite bone with endochondral growth at the condyle and intramembranous bone formation.
下颌骨宽度的增长
◆下颌骨外侧面增生新 骨，内侧面吸收陈骨； ◆髁突随颞凹向两侧生长，使 升支宽度增加； ◆下颌骨前部在乳牙萌出后， 宽度较少增加，下颌尖牙间 宽度在１１岁以后几无增加。
下颌骨高度的增长
◆ 下颌升支高度的生长主
◆ The mandibular condyleEndochondral growth by interstitual and appositional proliferation of cartilage
displacement of the mandible inferiorly and vertical
dimension for alveolar growth. ◆ A moveable articulation during various growth
changes.
下颌支的骨改建机制 (remodelling)
◆ 终末平面以垂直型及近中型较多，对恒牙合的
建立意义较大；
◆ 上颌乳尖牙的近中舌侧面与下颌乳尖牙的远中
唇侧面相接触。
（二）替牙合期
６-１２岁，“丑小鸭”阶段
Period when both primary and permanent teeth are present in the
mouth.
恒牙萌出时间及顺序
coronoid process become fully differentiated
◆ Alveolar process(intramembranous)
-Grows when teeth begin to erupt -resorbs when teeth are lost
The combination of condylar and ramus growth brings about:
months.
乳牙列间隙变化
◆ 生长间隙：３-６岁，前牙部分；
◆ 灵长间隙(primate space):
上颌乳尖牙近中或远中。
In the maxillary arch, the primate space is mesial to the canines. In the mandibular arch, the primate space is distal to the canine.
Spacing in the primary incisor region is normally distributed among all the incisors, not just in the “primate space” locations where permanent spaces exist in most mammalian species.
The mandible appears to “grow” in a downward and forward manner when visualized on superimposed serial cephalometric tracing registered on cranial base. A: Simultaneous displacement occurs in the opposite direction, displacing the chin anteriorly and inferiorly. B: Actual growth takes place in a wide variety of regional direction with the predominent growth trend posteriorly and superiorly.
下颌骨的三向生长
◆ 长度的增长
◆ 宽度的增长
◆ 高度的增长
下颌骨各部分的生长方向
（Enlow，DH，1990）
下 颌 骨 长 度 增 长
◆ 下颌升支前缘吸收陈 骨、后缘及外侧增生新骨； ◆ 下颌骨外侧增生新骨、内 侧吸收陈骨； ◆ 下颌骨的增长，以磨牙区 为最多，由第二乳磨牙至下颌 角的距离，在新生儿约为 10mm，６岁时约20mm， 成人约45-50mm。 ◆ Posterior border of ramusintramembranous bone formation by periosteal tissues. Simultaneous resorption of bone on the anterior border of ramus. ◆ Surface deposition and reposition on complete surface of mandibular- remodelling. ◆ Mandibular lingual tuberosity (intramembranous)-appositional growth for horizontal elongation of the mandibular body on the lingual surface(between most posterior molar and mandibular foramen)
关节部的生长与改建
◆ 髁突向后上方生长，形
成头大颈小的形态；
◆ 髁突的位置根据Ｖ字形
原理，向Ｖ字开阔的侧方 生长。 髁状突的生长
（Goose，DH，1982）
髁状突软骨的作用
Severe
mandibular
deficiency from TMJ infection.
颏部的生长
◆
灵长类中只有人类具有颏的特征；
要靠下颌髁突新骨的生长； ◆ 喙突的同时生长；
◆ 下颌体的生长，主要是靠 ◆ Surface deposition and resorption on complete 下颌牙齿萌出时牙槽突的增高 surface of mandibular-remodelling 及下颌骨下缘少量增生新骨。 inferior border of mandible
Class I relationship. (ii) Straight(Flush) terminal plane: erupting lower first permanent molars may give mesial force moving lower second primary
molars forward to allow a Class I molar relation.
（三）合的发育阶段
◆ ◆ ◆ 萌牙前期的颌间关系 乳牙合 替牙合
◆ 恒牙合
乳牙合期
◆ 第７-８个月时下颌乳中切牙萌出，在２-３岁时上颌 第二乳磨牙萌出，到３岁半时，乳牙牙根形成。 ◆ 一般萌出顺序为： I II IV III V
Sequence of eruption of primary teeth: Central & lateral incisors 6-9 months, first molars, canines 12-18 months, second molars 20-24 months. Mandibular teeth usually precede maxillary teeth by 1-4
The remodelling mechanism involved in this superior and lateral relocation is basically the expanding “V” principle. As the coronoid termini become higher, they grow apart at their apicies.
(iii) Late mesial shift of a straight terminal plane. -most common way that a Class I molar relation results. -permanent molars erupt end-to-end. -because of dimensional differences between the primary and permanent 3,4 and 5(Leeway space of Nance), after exfoliation of the primary teeth the lower first permanent molars move mesially
At birth: Body is still defined. Alveolar process scarcely present. Rami are proportionally short. Condyles are poorly defined.
Symphyseal growth still occurs increasing width
Gives the key to the occlusion
Three ways a Class I molar relationship can develop:
(i) Mesial step terminal plane: permanent molars erupt directly into a
或为：上：6-1-2 -4-3-5-7 -8 下：6-1-2 -4-3-5-7 -8
The sequence of eruption of the permanent teeth is more important than the exact time of eruption.
Eruption of the first permanent molars
下颌升支肌肉附着处的横 断面（Enlow， D.H.1990）
Vertical section through the ramus and the coronoid process showing the charateristic pattern of resorption
下颌支向侧方 扩大，“Ｖ” 字形原理
Most common eruption sequence:
上：6-1-2 -4-5-3-7 -8 下：6-1-2 -3-4-5-7 -8
5-8.5 yrs. early mixed dentition 9-13 yrs. late mixed dentition 18-25yrs
Another sequence of eruption fairly common in the mandibular arch is:
终末平面的类型
◆ 垂直型(flush terminal plane) ◆ 近中型(mesial step) ◆ 远中型(distal step)
正常乳牙合的特征
2-4岁 4-6岁 无间隙、无磨耗、E远中呈直线 有间隙、有磨耗、E 近中移动
正常乳牙合的特征
◆ ◆ 前牙合关系：覆盖很浅，覆合较深； 前牙部分具有生长间隙及灵长间隙；